The present invention relates to a rig for drilling or maintaining oil wells.
In recent years, in the field of drilling oil wells, there has been a more pressing need for rigs for the drilling or maintenance of oil wells themselves which present structures of easy and simple assembly and dis-assembly in relation to the oil wells in such a way as to maximise the production times of drilling and to minimise the non-productive times relating to erection and disassembly.
The American patent No. U.S. Pat. No. 3,942,593 makes known a drilling rig for oil wells which comprises:                a base structure which comprises a support platform on the ground and a raised work platform;        a deck which is co-planar to and integral with the support platform which is suitable for housing a trailer;        a telescopic antenna which is provided with two fixing pins which are arranged at the lower ends of the telescopic antenna itself in order to be engaged on the work platform; and        a lifting device which is suitable for lifting the telescopic antenna from a transport position, in which it reposes on the trailer with the two fixing pins at a level which is lower than the level of the work platform, to a working position, in which it is vertically arranged on the work platform and in which the fixing pins are engaged in respective hinges.        
The lifting device comprises:                two cable linkages, which are suitable for being connected to the lower ends of the telescopic antenna, and which are activated opposite the work platform in relation to the telescopic antenna itself in order to unite the fixing pins with the relative hinges; and        two hydraulic pistons, which are interposed between the telescopic antenna and the deck, and which are suitable for being elongated in order to rotate the telescopic antenna around the respective pins in such a way as to lift the telescopic antenna itself into its working position.        
The rig which is described in the above-mentioned American patent presents some limitations which are due both to the use of the cable linkages, which require considerable power in order to drag and lift the telescopic antenna as far as to make the fixing pins reach the hinges on the work platform, as well as the hydraulic pistons, the elongation and lifting capacities of which are such as to require structures of considerable dimensions.